Applying of classic parameters of cardiorespiratory exercise testing to identify high-risk patients in thoracic surgery

The objective was to assess the significance of classical cardiopulmonary exercise testing (CPET) indicators to stratify the risks of cardiopulmonary complications after radical surgery for lung cancer.

Materials and methods. The study involved 185 patients with lung cancer aged (66 ± 9) years who have undergone surgery at the clinic of the Pavlov University in 2018–2023. The following indicators of the CPET included in the recommendations for predicting mortality and postoperative complications were determined and analyzed: metabolic equivalent of task (MET), oxygen consumption (V’O₂/kg, ml/min/kg, % of expected),

ventilatory equivalent for CO₂ (V’E/V’CO₂). Statistical analysis of the data was carried out: intergroup differences were assessed using the Student t-test, prognostic significance – the Mann–Whitney U-test, and the separating value – the Youden index.

Results. No dependence was found between the development of complications and the achieved MET values (p = 0.513), as well as V’O₂/kg (peak) (p = 0.688), V’O₂/kg (AT) (p = 0.707), V’O₂/kg (peak)% of expected (p = 0.617). Significant differences in V’E/V’CO₂ were found at the anaerobic threshold (AT) stage: the probability of complications in patients with V’E/V’CO₂(AT)≥ 32.649 was 3.221 times higher (95% CI: 1.304 – 4.571).

The sensitivity and specificity of the model for V’E/V’CO₂ were 69.8% and 60%, respectively. V’E/V’CO₂ is also informative at the free pedaling (FP) stage. The odds of cardiopulmonary complications were 3.286 times higher with V’E/V’CO₂ (FP) ≥ 37.874 (p > 0.001). V’E/V’CO₂ retains its significance after unloading at all stages of recovery (R1, R2, R3). In the risk group patients with V’E/V’CO₂ (B1) ≥ 34.274, complications developed in 37.3% (p > 0.001), with V’E/V’CO₂ (B2) ≥ 37.533 in 38.8% (p > 0.001), with V’E/V’CO₂ (B3) ≥ 38.508 in 32.6% of cases (p = 0.007).

Conclusions. Contrary to accepted recommendations for predicting mortality and cardiopulmonary complications after surgical interventions, the values of MET, as well as V’O₂/kg (peak) and V’O₂/kg (AT) were not informative for risk stratification in thoracic surgery. V’E/V’CO₂ in relation to cardiopulmonary complications is informative not only on AT, but also during free pedaling and recovery, which makes it available for assessing the functional reserves of comorbid patients with low exercise tolerance. 

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